Human rights groups poured scorn on Tuesday on a Tatmadaw investigation into alleged atrocities against Rohingya Muslims, branding it a “whitewash” and calling for UN and independent investigators to be allowed into Burma.

More than 600,000 Rohingya have fled to Bangladesh since late August, driven out by a counter-insurgency clearance operation in Rakhine State that a top UN official has called a classic case of “ethnic cleansing.”

Accusations of organised mass rape and other crimes against humanity were levelled at the Burmese military on Sunday by another senior UN official, who had toured camps in Bangladesh where Rohingya refugees have taken shelter.

Pramila Patten, the UN special representative of the secretary-general on sexual violence in conflict, said she would raise accusations against the Burmese military with the International Criminal Court in the Hague.

The military, known as the Tatmadaw, has consistently proclaimed its innocence, and on Monday it posted the findings of an internal investigation on the Facebook page of its commander-in-chief, Senior-General Min Aung Hlaing.

It said it had found no instances where its soldiers had shot and killed Rohingya villagers, raped women or tortured prisoners. It denied that security forces had torched Rohingya villages or used “excessive force.”

The military said that, while 376 “terrorists” were killed, there were no deaths of innocent people.

“The Burmese military’s absurd effort to absolve itself of mass atrocities underscores why an independent international investigation is needed to establish the facts and identify those responsible,” said Brad Adams, Asia director at Human Rights Watch, in a statement.

The military’s self-exoneration came as US Secretary of State Rex Tillerson prepared to visit Burma on Wednesday for talks with the country’s leaders.

Tillerson and Aung San Suu Kyi, the head of a less than two-year-old civilian administration that has no control over the military, met in Manila on Monday, where they were both attending a regional summit.

With US senators in Washington pressing to impose economic sanctions and travel restrictions targeting the military and its business interests, Tillerson is expected to deliver a stern message to Burma’s generals, while supporting the transition to democracy.

Guterres, addressing the summit, described the exodus of refugees from Burma as a “worrying escalation in a protracted tragedy” and a potential source of instability and radicalisation in the region.

Canadian Prime Minister Justin Trudeau also he had an “extended conversation” with Suu Kyi about the plight of Rohingya Muslims.

“This is a tremendous concern to Canada and to many, many countries around the world,” Trudeau told a news conference in Manila.

While world leaders wrung their hands, thousands of Rohingya remained stranded in Burma, on beaches around the mouth of the Naf River, hoping to find a boat to make the short, sometimes perilous crossing to Bangladesh.

More than 200 have drowned making the attempt in the past couple of months and Bangladesh border guards have clamped down on fishermen who Rohingya were paying to take them across.

With fewer boats available, desperate Rohingya have been stringing together rafts from bamboo and plastic canisters. In the past week, some 1,200 people crossed over on such flimsy rafts, according to police.

“They’re still coming, risking their lives, driven by fears of starvation and violence,” Shariful Azam, a police official in Bangladesh’s Cox’s Bazar, a narrow spit of land where the world’s most urgent humanitarian crisis is unfolding.

The government in mostly Buddhist Burma regards the Rohingya as illegal immigrants from Bangladesh.

Suu Kyi’s failure to speak out strongly over the plight of the Rohingya has widely damaged the Nobel Peace Prize winner’s reputation as a stateswoman.

Many diplomats, however, believe Burma’s fragile transition to democracy after 49 years of military rule would be jeopardised if she publicly criticised the armed forces.

On Friday, the Burmese military replaced the commanding officer in Rakhine State. No reason for Major General Maung Maung Soe’s transfer was given, but a senior officer with the military’s media department told Reuters the general had no new assignment, and had been placed on a reserve list.

A spokeswoman for the US State Department, Katina Adams, said the United States was aware of reports of the general’s replacement.

“We remain gravely concerned by continuing reports of violence and human rights abuses committed by Burmese security forces and vigilantes. Those responsible for abuses must be held accountable,” Adams said.

Amnesty International also dismissed the military’s internal investigation and called for a UN fact-finding mission and for other independent investigators to be given full access to Rakhine.